Compared with HC, IL-18, IL-6, and ferritin were markedly elevated in active AOSD patients (Log2 fold changes, 8.86, 8.34, and 4.30, respectively) and in severe COVID-19 patients (Log2 fold changes, 2.73, 6.97, and 1.97, respectively). Here, IL18 is linked to adult-onset Still disease.